The present invention relates to a separating device for separating a first liquid from a second liquid and, wherein the first liquid has a lower specific density than the second liquid.
Such separating devices are necessary in compressed-air applications, for example. Air compressors generate compressed air by taking in and compressing ambient air. The contained air moisture condenses due to physical conditions and the drying of the compressed air. This condensate is a type of sewage that in most cases must not be discharged into the public sewer because it contains air compressor lubricants, and therefore the permissible hydrocarbon concentration limits are exceeded.
A volume flow rate of 60 m3 of intake air per hour may result in a mostly discontinuous condensate flow of 1.6 l/h that may be loaded with 300 mg of oil per hour which is equivalent to 190 ppm. There are different forms of bonding between water and lubricant, ranging from oil/water mixture via dispersion to emulsion. In Germany, the permissible amounts for discharge into a sewer are 20 or 10 ppm, in some cases 5 ppm. Thus, the condensate represents hazardous waste the disposal of which is expensive. That is why various methods and devices have been developed for separating the contained oil from the water.
Devices for separating liquids or dissociating devices for dissociating liquids are known. For example, utility model DE 90 040 19.8 describes a device for sucking off light liquid separated in a liquid separator. Said liquid separator comprises a housing in which a receptacle is arranged. A bag filled with an oil-binding agent is arranged in the receptacle. The oil-binding agent is a floatable granulated material based on polyurethane foam. The sewage contaminated with light liquid enters the housing through the entrance port. As long as the oil-binding agent in the receptacle is largely unsaturated, the receptacle only slightly immerses in the light liquid layer. The light liquid penetrates the receptacle and the bag containing the oil-binding agent and is adsorbed by the oil-binding agent. With the increasing saturation of the oil-binding agent, the weight of the bag is also increasing so that the receptacle is continuously sinking. When the receptacle reaches its lowest position, the oil-binding agent is largely saturated with light-density material and the bag may be replaced. The non-adsorbed liquid escapes through an outlet. Basically, the principle of this device is useful, but the device itself is very costly and susceptible to failure. For example, there is no guarantee that the entire volume of the liquid mixture actually flows through the bag so that complete filtering is not inevitably ensured.
On the basis of this device, DE 600 04 523 D2 also describes a dissociating device and a dissociating method for dissociating liquids of different densities. Basically, the device described therein operates according to the same principle, i.e. that an adsorbing material is saturated with one of the two liquids and sinks in the other liquid because of that. However, an essential difference is that in this device the entire volume flow must pass through the dissociating component that consists of an adsorbing material. The dissociating component is arranged within a receptacle in such a manner that it completely fills the cross-section of the receptacle. However, the friction between the dissociating component and the receptacle is a disadvantage of this device. With the increasing adsorption or contamination of the dissociating component and because of temperature and pressure variations, the frictional conditions are also changing which has an influence on the filtering process and the required expenditure of energy. Thus, the device is susceptible to failure and may require more maintenance.
Another disadvantage of the described devices is that they are not capable of treating highly dispersed or even highly emulsified condensates. Usually, more costly methods must be used, such as membrane, evaporating, or cracking methods.